"Londoners cannot trust Ken Livingstone with their money and in his last bid for power he will do and say anything to get back into City Hall," a spokesperson in the Boris camp said.

"His claims are not only fraudulent, they present a very real risk to the future prosperity of London, putting both jobs and economic growth at risk."

The Tories claim Ken would need to increase fares by 38% over the retail price index in 2015 to maintain current investment if he went ahead with plans to cut fares in the short term.

In all probability, the mayor would have to cancel many of the current investments planned for the tube lines in a bid to keep prices down during times of austerity - a choice many Londoners might sympathise with.

Meanwhile, Ken's team seized on the omissions in Boris' manifesto, saying they proved the incumbent was only interested in helping the privileged.

The manifesto contained no mention of gay and lesbian Londoners, faith communities, childcare or child poverty, the Labour camp said.

A poll for the Evening Standard yesterday showed over a third of Londoners believe Boris cares more about the privileged than ordinary Londoners, but that he continued to outperform Ken.